people = 20
cats = 30
dogs = 15

if people < cats
  puts "Too many cats! The world is doomed!"
end

if people > cats
  puts "Not many cats! The world is saved!"
end

if people < dogs
  puts "The world is drooled on!"
end

if people > dogs
  puts "The world is dry!"
end

dogs += 5

if people >= dogs
  puts "People are greater than or equal to dogs."
end

if people <= dogs
  puts "People are less than or equal to dogs."
end

if people == dogs
  puts "People are dogs."
end
#在这个里面也就是提供了一些真值语句，if 的作用就是当此条件为真时，就输出这些字符串，为假就不输出了，前面的真值表里面的东西都做过了,后面让dogs = dogs + 5就重新定义值再来进行比较，提值
